The present invention relates to a slat and method for constructing slats which is efficient, warp resistant, saving of natural resources, and longer slat of natural materials without warping, to enable the construction of a high quality, consistent louver product of any practical dimension.
Slats are utilized in a variety of window coverings, including Venetian blinds, and vertical blinds. Slats have in the past been constructed of thin metal from rolls, curved along the path of their shorter dimension to produce a break through stiffness, holding stiff unless stressed. More recent slats include relatively thicker structures whose stiffness is similar to that of a ruler. Modern materials have enabled the construction of slats having a wide variety of strength and size, and other attributes associated with the materials from which they were constructed.
Slats constructed of such synthetic material have a main disadvantage of cost, both through raw material scarcity and processing time. Carbon based materials can require pressure based formation as well as consideration relating to sizing shrinkage and other dimensional accommodation.
Natural materials, especially wood, are uneven and tend to warp. Warping in long slats is especially pronounced during periods of humidity change. Formation in one humidity environment followed by installation in a different humidity environment will typically result in twisting, bending, and general un-evenness. Further, the effects may occur at different locations along the length of the slats, and such effects cannot typically be defensed against by treating or sealing, as most materials are permeable to moisture. Selection of lengths of wood of even grain creates an even more severe materials problem as the reject rate for material rises and the costs rise further.
Furthermore, in the construction of wood slats, there occurs a consistent level of waste based upon statistical differences between the lengths of raw material and the lengths and processing requirements for the individual slat sizes. This waste is extremely significant and contributes to the overall cost for natural slats. Where waste material has a longitudinal (with the grain, for example) size which is less than the minimum length slat, it is disposed of as scrap or refuse. Such scrap is significant in the slat production process and not only drives up cost, but results in a wasting of natural resources by causing more natural resources than are absolutely needed for the slats as being spent.
Utilization of absolute small sized scrap has been had by further costly processing as by making of press board and composites which are dependent upon costly processing, and do not lend themselves to use with slats since the bending strength must extend over a long length, much like a ruler or yardstick. There is a further waste in such scrap as utilization in press board requires further cutting and chipping and further destroys the structural integrity of the material structure present. Beyond press board, the only other value of such small scrap is the thermal value on burning.
A final problem is the extent to which wood scrap can be used to form slats which have a finished wood appearance. Where users want slats which have a natural wood appearance, as if the slat were cut from a continuous length of grained wood, the resources otherwise utilized would be even higher. What is needed is a method which enables wood scrap to be utilized to form a slat which has more of a natural wood appearance to avoid the even more inefficient practice of providing a slat from a whole length of starting wood material.
The structures and process for producing the structures of the invention enable extensive and efficient use of block scrap for slat manufacturing. The techniques employed advantageously accomplish two goals simultaneously. The technique enables scrap, such as block scrap, to be formed into longer effective lengths. Such longer effective lengths can then be cutably formed into slats of various sizes. The joinder of the block scrap is by deeply extending, finite interlock length finger joints which, once the material is cutably formed into slats, remain as relatively shallow (the thickness of the slat) and finite interlock length finger joints. The joints have the added benefit that they statistically xe2x80x9cbreak upxe2x80x9d any grain differences which would otherwise create warp, and enable long lengths of slat to be employed from several shorter lengths of scrap. The utilization of multiple sets of finger joints virtually completely eliminates the tendency to warp, and provides additional strength against twist forces. Further, as an added economic benefit above and beyond the benefits already mentioned, the technique not only enables waste normally occurring in slat manufacture to be saved, but actually encourages the manufacture of a superior quality product by encouraging lower cost scrap to be used as the primary resource in the manufacturing process. In other words, longer lengths of higher priced wood can be used elsewhere in products where grain structure and uninterrupted length is necessary, and thus drive down the costs in those industries, while at the same time enabling slat construction almost exclusively from scrap.
To further utilize scrap wood and to further reduce waste, adjacent narrower widths of wood can be utilized in combination with wider lengths of wood at the finger joint to enable two or more widths of wood material to function as if they were a single width of material. When securely glued, both at the finger joint as well as along the lengths of more narrow material, the resulting slats have as much strength as slats formed from a whole length of wood material. Even where the narrow lengths of wood have a linear, thin, glued interface, superior strength bending and twist resistance is observed.
A technique for covering the constructed slat with a layer of paper, especially paper bearing a wood grained pattern, followed by use of a gluing material of, for example vinyl acetate resin, followed by providing a clear and appropriately surface finish varnish, preferably of ultraviolet resistant material can produce a slat which has an appearance exactly as if it were formed from a single length of wood material.